Spark-plug.



M. G. KOPP.

SPARK PLUG.

APPLIGATION FILED NOV. 8. 1912.

Patented Feb. 3

UNITED STATES PATENT onnrcn.

MELROSE G. KOPF, 0F DAYTON, OHIO, ASSIGNOR 1'0 MoCORMiCK MANUFACTURING COMPANY, OF DAYTON, OHIO.

' SPARK-PLUG.

Specification of Letters Patent.

Patented Feb. 3,1914.

Application filed November 8, 1912. Serial No. 780,187.

tain new and useful Improvements in Spark-Plugs, of which the following is a specification.

The main objects of this invention are to provide an improved form of power spark plug, for use in internal combust1on e11- gines, constructed so as --to be more positive and efiicient in its operation; to provide an improved form of electrodes for spark (plugs whereby a multiple of sparks are pro uced across the spark gap to provide an improved construction of the electrodes whereby they are practically unaffected by continuous operation; to provide electrodes of an improved shape and relative arrangement whereby the energy of the spark is conserved and the possibility of the accumulation of substances thereon, that would tend to prevent the spark, is practically eliminated; to provide an improved construction of the plug whereby an annular compartment is formed inwardly of the electrodes which constitutes a spark chamber communicating with the explosion chamber of the engine by means of the spark gap; to provide an improved construction of the surrounding walls of said spark chamber whereby the gas entering the spark chamher is concentrated and mixed; to provide improved means for supporting and securing the electrodes in positive fixed relation with respect to each other; to provide improved supporting means for one of the electrodes whereby it may be removed for the purpose of cleaning or replacing it without disconnecting any of the parts from the others; to provide an improved form of condenser adapted, in combination with the electrodes, to intensify the spark across the spark gap; and to provide an improved arrangement of the condenser within the spark plug.

An illustrative embodiment of this invention is shown in the accompanying drawings, in which Figure 1 is a quarter sectional elevation of the spark plug unit. Fig. 2 is a transverse sectional detail taken on the line AA of Fig. 1. Fig. 3 is a diagrammatic view illustrating the arrangement of the electrical connections between the condenser and electrodes, and their connection with the coil or magneto. Fig. 4 is a perspective ,view of the shell on which one of the electrodes is formed and which is secured within the lower end of the supporting bushing. Fig. 5 is a perspective view of the internal condenser plate.

In the construction shown in the drawings the metallic bushing or fitting 1 serves as a supporting member for the electrodes and condenser unit and is provided with threads 2 at its lower end by means c(@w'luch it is screwed into and thereby se ured to the engine cylinder 3.

The outer electrode is in the form of an inwardly projecting annular shoulder 4 integrally formed within the lower end of the shell 5. The shoulder 4 is of substan tially uniform V-shape cross section in all radial planes and has its inner face substantially at right angles to the axis of the shell and the outer face tapered or inclined upwardly forming a conical opening and providing a knife edge 6 at the crest of the shoulder. The other or-central electrode is in the form of a cone 7 secured to the lower end of the rod 8 supported within the insulating stem 9. The cone 7 is concentrically arranged within the shell 5 in an inverted position with its base and apex located on respectively 0 posite sides of the knife edge 6. The annu ar V-shaped shoulder and the cone are thus arranged so that the elements of the cone converge in the opposite general direction from that in which the elements of the conical surface of said V-shaped shoulder converge. The diameter of the base of the cone is substantially equal to the diameter of the opening formed at the crest of the V-shaped shoulder. This will permit the cone to be ad justed with respect to the shoulder so as to vary the size and area of the spark gap. The rod 8 is secured within the stem 9 through being screwed into the end of the rod or bolt 10 located at the upper end of the stem and having a cap 11 which fits over the end thereof. A layer of asbestos cement 13 is placed between the base of the cone 7 and the stem 9, and between the cap 11 and the stem for further securing the parts together and for taking up the difference in expansion.

The insulating stem 9 is preferably made of porcelain and is supported within the bushing 1- by means of the annular shoulders or ledges l4 and 15 respectively formed on the stem 9- and bushing 1. In order to provide a gas tight joint at this point a copper-asbestos washer 16 of the usual construction is interposed between the shoulders 14 and 15. The stem 9 is rigidly secured in position by means of the nut 17 which is screwed into the bushing 1 and which has a depending annular flange 18 provided with an annular beveled shoulder 19 adapted to engage the annular beveled shoulder 20 formed on the stem 9 above the The arrangement of these beveled shoulders 19 and 20 makes it possible for the stem to be rigidly secured in position with but a small area of contact between the nut 17 and the stem 9, thereby .avoiding the possibility of the stem 9 not 3 being properly arranged because of its not being perfectly. true in construction, as would probably be the case if the parts had a larger area of contact. Also by having a small area of contact there is less interference with a free expansion of the porcelain stem when it becomes heated and thereby avoids the possibility of the stem becoming cracked.

The lower end of the stem 9 is tapered and there is therefore provided an annular spark chamber 22 surrounding the electrode 7 inwardly of the electrode 6, and which by way of the contracted spark gap 23 communicates with the explosion chamber of the engine cylinder. During the compression stroke of the engine to which a spark plug of this constructlon is attached, the gaseous mixture is forced into the spark chamber 22 and due to the shape and relation of the with the warm electrodes it becomes thoroughly mixed with some of the remaining warm gas of the previously exploded mixture and is further heated by intimate contact with the heated walls of the spark chamber. It has been found that this mixing of the fresh gases ases remaining from the previously explo ed charge and their intimate contact with the heated walls of the spark chamber, conditions the entire gaseous gases within the explosion chamber.

eanna? 4 charge of sparks across the gap and before any of the energy is dissipated. The sparks do not always occur at the same points but take place in a direction upwardly toward the base of cone of the central electrode 7 and within the spark chamber and travel around the gap in a rotary manner.

Although t e central electrode projects without the annular one, the spark occurs upwardly across the opening which provldes for communication between the spark chamber 22 and the explosion chamber of the engine, where its force is spent in igniting the gaseous mixture within the spark chamber.

The small quantity of wellmixed gases being subjected to such a confined and in tensified spark are instantaneously exploded in a more thorough manner than is possible where the spark occurs unconfined and unprotected in a large quantity of gas. These gases after being exploded in the spark chamber 22 expand and cause a jet of flame to shoot into the explosion chamber of the engine where it causes the explosion of the gases therein. The result is a more positive explosion of said gases than is possible where reliance for ignition thereof is had upon the spark alone, as is the case with the spark plug of the usual construction, A further result is that a more nearly complete combustion of saidgases is effected thereby decreasing the fuel consumption and increasing the power of expansion.

Even though a more nearly complete combustion of all the gases is'obtained with the use of this spark plug, yet there is always the ossibility of unconsumed particles, particu arly of some foreign substance, remaining in the engine cylinder, which have a tendency to be deposited on the electrodes, but the passage of the gases into and out of the spark chamber 22 will tend to prevent this deposit. During the inrush of the gases into the spark chamber they strike the upwardly ta cred surface of the shoulder 4 and are de' ected against the cone 7, and from the cone 7 into the spark chamber 22 thereby dislodging any substance which might have a tendency to adhere to either of the electrodes. As the gases are ignited within the spark chamber 22 and rush out therefrom, they are deflected against the cone 7 thereby further aiding in the keeping of the electrodes free from'deposits. A material advantage of the prevention of the continuous carbonizing on the stem 9 is that no electrical energy is dissipated by leakage and that all of it is conserved for intensifying its passage across the terminals. Should any oil accumulate on either of the terminals, it will travel down along the inclined surfaces thereof, from which it will be dislodged through a general movement of the The action of the sparks on the knife edge also tends to keep the electrodes free from deposits of oil and carbon.

The electrodes have a suiiicient mass of material in themselves, and are in intimate mechanical contact with a larger surrounding mass so that'heat produced by the continuous sparking is readily conducted away from the points, and thereby avoids the possibility of the points burning away because of the intense heat to which they are subjected. The rotary movement of the sparks between the electrodes, constantly playing between changing points on the cone 7 and the shoulder 4:, prevents the concentration of the sparks between fixed points as in the case with the usual spark plugs and thereby prevents the destruction of the electrodes. The gradual consumption of the electrodes constituting the spark gap in plugs of the usual construction, results in the gradual diminution of engine power due to the increased distance of the gap, and finally results in the complete failure of the spark. These parts, therefore, require less attention and less frequent renewals than spark plugs which use one or more wire electrodes, or the like.

The shell 5 is made removable from the bushing 1 in order to facilitate access to the electrodes without necessitating the dismantling of the entire plug. This construction also has the advantage of making it possible to readily substitute another outer electrode and be sure that it will be properly positioned, with respect to the cone, without requiring any adjustment of the other parts. The shell is secured in position within the bushing by means of the pin or shoulder 24 and bayonet slot 25.

In order to intensify the spark across the spark gap 23, and thereby increase the efiiciency of a spark plug constructed as hereinbefore described, a condenser is arranged within the spark plug unit and connected in shunt with the electrodes, which acting to gether form a distinct electrical circuit producing results hereinafter described. By experiment it has been found that a condenser, constructed in the manner now to be described, produces the most efficient results with electrodes of the design herein shown and described, and that such a condenser automatically lends itself to varying conditions met with in using the spark plug on ignition systems of various sizes and kinds. The condenser includes a cylindrical dielectric 26, open at one end and preferably made of porcelain. This dielectric embraces the stem 9 and is provided at its upper end with an outwardly and downwardly extendingflange 27, by which it is supported on the cylindrical housing 28, which in turn is supported on the nut 17. The outer plate 29 of the condenser is preferably in the form of tin-foil extending almost the entire length of the dielectric and secured thereto by means of shellac or other adhesive substance which will not be aflecte'd by heat. The mner' plate of the condenser is in the form of a cylindrical shell 30, preferably made of some such resilient material as tin. The

shell 30 is provided with a longitudinal slit,

31, which not only renders it convenient to be easily inserted into the dielectric 26, where it is retained through frictional engagement therewith, but also assists in the automatic action mentioned above. The interior wall of the dielectric is not likely to be perfectly true, nor will the shell 30 closely conform to the shape of the dielectric, so that when the shell 30 is in position in the dielectric there is an air space or air pockets between the op sed walls of the dielectric and shell. .By eviating from the usual construction of condensers, wherein the inner plate is continuous and also secured to the dielectric by means of shellac, and merely slitting and securing the interior plate within the dielectric through frictional engagement, I have found that better results are obtained in its use with spark plugs, particularly one of this construction. The reason for this I cannot explain other than to say that it is probably due to some high frequency, or high potential discharge phenomena not yet thoroughly understood.

The exterior plate 29 has its upper edge flanged over so as to contact with the protecting shell 28 surrounding the dielectric. The shell 28 rests upon the nut 17 and thereby forms electrical connection with the electrode 6 by way of the bushing l. The interior shell is provided with a transversely disposed tongue 32 having an aperture 33 through which the rod 10 extends and which aflords metallic contact therewith, whereby it is electrically connected to the electrode 7 through the medium of the rod 8. The shell 30 may also be placed so that the tongue rests upon the cap 12 so as to insure a better metallic contact with the parts connecting it electrically with he electrode 7 The dielectric 7 and shell 28 are held in their respective positions by means of the nut 34 screwed onto the binding post 10.

unit combining the condenser and specific electrodes as herein described, when energized by the coil or magneto produces a plurality of intense conserved and high frequency sparks of such a wave-length that none of the energy is dissipated. The character of the discharge from this condenserelectrode circuit aids in the rapid dissociation of the gases and thereby increases the flame propagation. It has been found that due to the mechanical and electrical design of this spark plug that the process of exploding the gases makes it possible to explode mixtures within wider ranges of quality and compression than with plugs of the usual construction. The difference in operation between this. and other spark plugs has been herein explained in the description of the several features of this plug.

Although but one specific embodiment of this invention has been herein shown and described, it will be understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of this invention as defined by the following claims.

I claim:

1. In a spark plug, the combination of a supporting member, an inwardly projecting annular shoulder of substantially V-shaped cross-section formed adjacent to the lower end of said member and constituting one electrode, and a cone constituting the other electrode located with the base and apex thereof on respectively opposite sides of the crest of said annular shoulder, said cone and shoulder being concentrically arranged so that the elements of the cone converge in the opposite general direction from that in which the elements of the conical surface of said V-s haped shoulder converge.

2. In a spark plug, the combination of a supporting member, a shell adapted to be secured within the end of said member, an interior annular shoulder on said shell hav ing the inner face thereof substantially at right angles to the axis of said member, and having the outer face inclined inwardly so as to provide an annular knife-edge shoulder, and an inverted cone concentrically arranged within said shell with the apex thereof extending below said knife-edge.

3. In a spark plug, the combination of a supporting member, a pair of electrodes carried by said member, a condenser arranged to coact with said electrodes, said condenser comprising a hollow dielectric having an irregular internal surface, an exterior metallic plate secured to said dielectric, a metallic shell supported within said dielectric against said irregular surface and providing air spaces between said shell and dielectric, and means connecting said condenser in shunt with said electrodes.

4. In a spark plug, the combination of a supporting member, an inwardly projecting annular shoulder on the-inner end of said member and constituting one of the electrodes, an insulating stem secured within said member, a rod incased in said stem, and an enlarged cone carried by said rod at the end of said stem in an inverted position and constituting the other electrode said cone' being concentrically arranged with respect to said annular shoulder with the base and apex located on respectively opposite sides thereof.

5. In a spark plug, the combination of a supporting member, an inwardly projectin annular shoulder formed on the inner en of said member and constituting one of the electrodes, an insulating stem secured within said supporting member, a cone carried on the end of said stem and constituting the other electrode, means for securing said stem in said member with said cone adjacent to said shoulder, a cylindrical dielectric em bracing said stem and supported on said means, an. exterior plate secured to. said dielectric, a metallic shell secured on the interior of said dielectric so as to have an air space between it and said dielectric, and means connecting said plate and shell with said electrodes.

6. In a spark plug, the combination of a supporting member, a supporting stem secured at its lower end in said member, electrodes respectively formed on said member and stem, a condenser supported on said member, said condenser comprising a hollow dielectric embracing the upper portion of said stem, and spaced away therefrom, a binding post secured to said stem and extending to the exterior of said dielectric, means eoacting with said post for securing said arts in their assembled relation, an exterior metallic plate secured to said dielectric, a resilient metallic shell held in said dielectric by frictional engagement therewith, a transversely disposed tongue on said shell adapted to engage said binding post and form metallic contact therewith, and means connecting said condenser in shunt with said electrodes.

7. In a spark plug, the combination of a supporting member, a supporting stem secured at its lower end insaid member, electrodes respectively formed on said member and stem, a condenser supported on said member, said condenser comprising a hollow dielectric embracing the upper portion of said stem, and spaced away therefrom, a binding post secured to said stem and ex tending to the exterior of said dielectric, means coacting with said post for securing said parts in their assembled relation, an exterior metallic plate securedto said dielectric, a resilient metallic shell held in said dielectric by frictional engagement therewith a transversely disposed tongue having an aperture therein adapted to receive said binding post for forming metallic contact therewith, and means connecting said condenser in shunt with said electrodes.

8. In a spark plug, the combination of a supporting member, an insulating stem secured within said member, electrodes respectively formed on said member and stem, a part embracing said stem and supported on said member and coacting therewith to form a housing for said stem, a binding post secured to said stem and extending to the exterior of said part, a nut adapted to be screwed onto said stem to engage said part for holding the same on said member, a lock nut ada ted to be screwed onto said stem outward y of said first nut and a spring interposed between said nuts for'the purpose specified. Y

9. In a spark plug, the con'lbination of a supporting member, an insulating stem secured within said member, electrodes respectively formed on said memberand stem, a part embracing said stem and supported on said member and coacting therewith to form a housing for said stem, a binding post secured to said stem and extending to the exterior of said part, a nut adapted to be screwed onto said stem to engage said part for holding the same .on said member, a lock lut adapted to be screwed onto said stem outwardly of said first nut and having an annular recess therein, and a spring embracing said rod and housed in said recess for the purpose specified.

10. In a spark plug, the combination of a supporting member, a shell having a continuous annular wall removably secured within the end of said member, an inwardly projecting annular shoulder integrally formed within the lower end of said shell and constituting one electrode, an inverted cone concentrically arranged with respect to said shoulder and having the apex and base thereof located on respectively opposite sides of said shoulder and constituting the other electrode.

11. In a spark plug, the combination of a supporting member, an inwardly projecting annular shoulder of V-shaped cross-section formed on the inner end of said member and constituting one of the electrodes, an insulating stem secured within said member, a

rod incased in said stem, and an enlarged cone carried by said rod at the end of said stem in an inverted position and constituting the other electrode, said cone being concentrically arranged with respect to said annular shoulder with the base and apex located on respectively opposite sides thereof, the diameter of the base of said cone being substantially equal to the diameter of the opening formed at the crest of said V- shaped shoulder.

Signed at Dayton this 30th day of October 1912.

M. G. KOPF. Witnesses:

JOHN C. BAGGOTT, FRANK J. MCCORMICK, Jr. 

